One of the most interesting plot twists could be a character who was thought to be a minor noble rising to a key power figure. Maybe they discover a long - lost heirloom that gives them some sort of magical or political advantage. For example, a small - time knight finds an ancient sword that was once used by a great conqueror. This sword gives him the respect of the people and he starts to amass an army.
In fanfiction, some characters might have more altruistic motivations. For example, a character like Tywin Lannister, who was originally power - hungry in the official story, could be motivated by a desire to protect the smallfolk in the fanfiction. This would completely change his actions and how he interacts with other characters.
His sisters, Visenya and Rhaenys, are also probably popular. Writers could focus on their individual powers and how they influenced the conquest. For example, Visenya's more martial nature and Rhaenys' charm.
Perhaps a fanfiction where the magic in the conquest was more prominent. Instead of just using his dragons, Aegon has to also deal with powerful wizards and sorceresses from the different kingdoms. This would add a whole new dimension to the conquest story.
One interesting plot twist could be that Aegon has a secret alliance with a powerful magical being that no one in Westeros suspects. This being could help him in unexpected ways during his conquest, like using magic to disable the defenses of a stronghold just before Aegon's forces arrive.
One idea could be a story where Kratos finds himself in the world of Westeros. Maybe he gets involved in the power struggles between the houses. He could use his combat skills to fight against the White Walkers, bringing a whole new level of action to the fight against the undead.
Rhaenys Targaryen is another significant character. Her charm and diplomatic skills could be highlighted in the fanfiction. She might be the one who tries to win over the hearts of the people in the kingdoms they are conquering. For example, she could use her beauty and grace to make alliances with some of the minor lords who are initially hesitant to side with Aegon.
One main theme is the struggle for power. Just like in 'A Game of Thrones' where various houses fight for the Iron Throne, in the fanfiction set in the 'A War of Stars' universe, different factions might fight for control of a planet or a star system. Another theme is loyalty. Characters have to decide who to side with, whether it's their own family like in 'A Game of Thrones' or a particular group in the 'A War of Stars' context.
The desolate and harsh landscapes of God of War could be blended with the diverse regions of Westeros. For instance, the frozen wastelands where the White Walkers roam could be combined with the ice - covered areas in God of War. This would create a more extreme and dangerous environment for the characters.
One way is through the characters. Kratos could enter Westeros through a portal or some magical means. His brute strength and combat skills would immediately change the power dynamics. He could be a wild card in the wars for the throne.